This invention relates generally to electronic code keyers, and particularly relates to an improved electronic code keyer with completely automatic operation provided by a microprocessor.
Ever since the first code keyer was developed, the operator's goal has been to produce errorless text transmissions at high speed. But with more than 50 different characters typically involved in a standard message and with each character comprised of up to six bits of information in the form of dots and dashes, the memory and manual dexterity of even the most skilled keyer operator has been put to the test. During this period various approaches for minimizing operator error while simultaneously increasing message transmission speed have been attempted.
One approach to improving keyer operator efficiency is disclosed in U.S. Pat. No. 3,895,185 to Ramsey which makes use of a modified ring counter circuit for converting Morse or similar code signals to characters and storing them so that they can be read on a display panel as desired. This system utilizes a three position switch for the generation of dots and dashes in combination with individual character indicator lamps arranged in what is described as an inverted three configuration on a front panel which permits the character generated by virtue of the operator produced dots and dashes to be observed by the operator. The inverted tree-counter configuration includes a read only memory (ROM), or a diode matrix, which converts a serial asynchronous telegraphic-type code to a serial synchronous and parallel code for communication functions permitting the use of conventional multi-character printers or displays. The basic storage or latching circuits for the tree counter system provide for storage by locking on to the character required and turning on a series circuit indicator light in an individual anode circuit. The system therefore not only permits the character generated to be visually displayed but also provides for the temporary storage of generated characters which may be later transmitted. This store and transmit feature permits the operator to generate characters independent of the individual operating speed of the user. U.S. Pat. No. 3,564,139 to Bodenstein et al provides an arrangement for the very rapid consecutive operation of a two key impulse transmitter such as a telegraph transmitter without the introduction of any errors due to the closeness in time with which the keys are actuated. This system allegedly eliminates problems arising from the possible formation of so-called mixed symbols which generally are caused by erroneous impulse combinations due to the operation of two operating keys in rapid succession by apparently eliminating the possibility of such double key operations. Bodenstein employs storage means into which the impulses having a duration between two and three microseconds are transferred, with circuit means provided to terminate or transfer these impulses after a period of less than one or two microseconds. By thus shortening inpulse duration the possibility of simultaneous pulse overlap is apparently substantially reduced thereby precluding erroneous character entries caused by simultaneous double key operation.
A more recent advance in the art of electronic code keyers is embodied in a keyer produced by Advanced Electronic Applications, Inc. of Lynnwood, Wash. This keyer makes use o9f a random access memory in the form of an integrated circuit having the capacity to store 4,096 bits which is the approximate equivalent of 500 Morse code characters. Keyer entries are provided to a pair of coupled microprocessors which generate a sequence of characters based upon the coded inputs for storage in and recall from the random access memory. Thus, message text strings may be provided to and stored in a memory at essentially any desired coded impulse input rate and read out of memory and transmitted at a desired word output rate. This arrangement makes the transmission rate essentially independent of the operator's coded impulse input rate. This system, however, suffers from the limitation in that changes in keyer output mode of operation such as the rate at which words are transmitted, the inter-character or inter-word spacing, etc., can be changed only by means of manual inputs following the transmission of each individual message. Therefore, this system, while providing for a high degree of errorless message transmission, is of limited flexibility when a number of messages having a large variety of format parameters is required.
The present invention is intended to avoid the aforementioned electronic code keyer performance limitations by providing a keyer arrangement which permits the user to transmit coded message information over a very large word per minute rate range which is totally independent of the rate at which the operator provides the coded inputs. In addition, stored command strings permit sequential automatic operation of the keyer over a large range of message format parameters.